Logical ReasoningDifficulty: Medium

PT106 S2 Q11 Explanation

John works five days each week

A free, expert breakdown of this official LSAT Logical Reasoning question.

TopicsNecessary Assumption

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Stimulus

John works five days each week except when on vacation or during weeks in which national holidays occur. Four days a week he works in an insurance company; on Fridays he works as a blacksmith. Last week there were no holidays, and John was not on vacation. company on Monday, Tuesday, Wednesday, and Thursday last week.

What this question is testing

Necessary Assumption

Your task

Find the assumption the argument requires in order for its conclusion to hold.

Common trap

Answers that would help the argument but aren't strictly required (sufficient, not necessary).

Winning move

Negate each choice — the right one breaks the argument when negated.

Reading along? Open the full official question in LawHub — we show a fragment here and keep the reasoning in our own words.

The question
11.

Which one of the following is an assumption on which the

Answer choices

  1. Too Strong: never2% picked this

    John never takes a vacation of more than one week

    This argument is about a week in which John isn't on vacation, so the argument isn't assuming anything about what John does when he is on vacation.

  2. Out of Scope: entire workday2% picked this

    Every day last week that John worked, he worked for an

    The wording only talks about whether or not he works on a given day. It doesn't ever get into this new nuance of whether it's a partial vs. entire workday. At first I thought maybe this answer was aloofly getting at the "what if he worked at two jobs on Friday" objection, but it would need to be much more specifically tailored to that kind of language. If we negate this answer and say, "At least one day last week that John worked, he only worked for 80% of the workday", that wouldn't weaken anything.

  3. Premise Salad3% picked this

    John does not take vacations in weeks in which national

    This is just blending concepts from the premises, but it has nothing to do with what needs to be assumed in order to draw the conclusion that he must have worked M/Tu/W/Th. If we negated this and said, "John does sometimes take vacations during holiday weeks", that wouldn't weaken the argument at all, especially since last week was neither a vacation week nor a holiday week.

  4. Correct75% picked this

    Last week John worked neither on Saturday nor

    Why this is right

    The author is thinking, "Okay, he worked 5 days, 4 of them at insurance. Friday is gone because of blacksmithing, so he must have worked Mon/Tu/Wed/Thu." But why does it have to be those four days? Couldn't one or two of his four days been a Saturday or Sunday? The author is assuming "no". If we negated this answer, we'd be saying "John worked on Sat and/or Sunday of last week". That would badly weaken the argument, because there would be no reason to think that his four days at the insurance company were M / Tu / W / Th, if we knew that one or two of the five days he worked last week was a Saturday or Sunday.

    Skill tested: Necessary Assumption · how this choice captures the argument's function is the move to repeat next time.

  5. Too Strong: no days17% picked this

    There were no days last week on which John both worked in the insurance company and also

    Man, this is tempting, because this relates to our other objection, "What if John doubled-up on Friday?" However, this answer in that case should sound like this: "On Friday, John did not both work in the insurance company and also work as a blacksmith." This answer becomes too strong by precluding that from happening on no days. It's not an objection to the argument if, on Monday, John worked at both insurance and blacksmith. It's only an objection if it happened on Friday, since the author is using "blacksmith on Friday" to rule out "insurance on Friday". Does John only work at the blacksmith on Friday? We don't know. We were never told he works only one blacksmith shift per week. We were never told that he works as a blacksmith only on Friday. So the author doesn't have to believe that John never doubled-down on insurance/blacksmith on Mon / Tu / Wed / Thu. She only needs to assume he didn't double down on Friday.

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